Solvent refining of hydrocarbon oil



Patented Jan. 14, 1941 UNITED STATES PTENT OFFICE Leon W. Cook, Beacon, N. Y., assignor to The Texas Company, New York, N. Y., a corporation of Delaware No Drawing. Application June 18, 1937,

Serial No. 148,954

1 Claim.

This invention relates to refining hydrocarbon oil, and particularly to the solvent refining of residual lubricating oil fractions derived from petroleum.

The invention contemplates extracting hydrocarbon oil with furfural in the presence of chlorphenol. It has particular reference to extracting residual lubricating oil stock with these two solvents, whereby a lubricating oil product is produced having characteristics superior to those of a product obtained by extracting with the individual solvents alone. The product so obtained, for example, has a high viscosity index, coupled with a low residual carbon content.

Moreover, a higher yield of such oil can be obtained from the same stock by treating it in accordance with the method of this invention.

More specifically, the invention comprises extracting residual lubricating oil stock with furfural and chlorphenol, such as parachlorphenol,

or a mixture of para and orthochlorphenol comprising around 60 to 70% of the para compound.

' I have discovered that the addition of parachlorphenol, or a chlorphenol mixture consisting mainly of the para isomer, very greatly improves the effectiveness of furfural as an extraction solvent for residual lubricating oil stocks, particularly from the standpoint of producing a refined oil of low residual carbon content and of improved color.

Parachlorphenol exerts a comparatively high degree of solvent action upon the asphal'tic and dark-colored constituents of residual oils. At the same time, it also exerts selective action as between low and high viscosity index constituents of the oil, although in this respect, it is less selective than furfural, and particularly if the parachlorphenol has associated with it substantial amounts of the orthochlorphenol. The orthochlorphenol is substantially completely miscible with lubricating oil in all proportions at all temperatures above its solid point. Consequently, the ortho compound fails to exert selective action as between low and high viscosity index constituents of the oil. Its presence, therefore, impairs the selective action of the para compound, especially if present in large amount.

However, by the procedure of my invention, the lack of selective action possessed by the ortho constituent of the chlorphenol mixture is ofiset by the highly selective action of furfural. The furfural thus acts as an anti-solvent for the high viscosity index or paraffinic constituents of the My invention, therefore, combines a high degree of selective action as between low and high viscosity index constituents of residual oil with a high degree of solvent action upon the residual carbon-forming and dark-colored constituents of a the Oil.

As a result, by employing the solvent mixture (1) Furfural alone,

(2) Parachlorphenol alone, and

(3) A mixture of equal parts of furfural and parachlorphenol.

Table I shows the relationship between residual carbon content and yield of rafiinate when extracting with the three solvents:

TABLE I Carbon residue" content-Per cent by weight of Solvent Raffinate, percent by volume Parachlor- Furfural Furrm a1 phenol plus parachlorphenol *Conradson carbon.

The lubricating oil residuum had a residual carbon content of about 6.7% and, as indicated by the foregoing table, the ramnate obtained by extracting with furfural still had a high residual carbon content,- ranging from 5.4 to 6.0%. Where the raffinate amounted to of the residuum the residual carbon content was 5.4%, while in the case of a rafiinate amounting to of the residuum, the residual carbon content was 6.0%.

In contrast, when extracting with parachlorphenol alone, obtaining the same yields of raffinate, the residual carbon content ranged from 2.25 to 4.6%. Likewise, when extracting with a mixture of equal parts of furfural and parachlorphenol, the residual carbon content ranged from 2.6 to 4.7%, not greatly difi'erent than with the furfural absent.

With 50% furfural, it would be normal to expect the residual carbon content of the raffinate to lie midway between the values obtained with the individual solvents alone when extracting to produce the same yield. Contrary to expectation, however, the residual carbon content of the raffinate produced with the mixed solvent is almost as low as with parachlorphenol alone.

Table II shows the relationship between vis- I cosity index and yield of rafiinate when extracting with the three solvent liquids.

TABLE II Viscosity index of rafiinate (Dean & Davis) Solvent Ralrlnate, percent by volume Parachlor- Furfural Fun-11ml phenol plus parachlorphenol (3) Table II shows that, when extracting with furfural alone to produce a rafiinate amounting to 55% by volume of the residuum, such raninate will have a. viscosity index of above 90, and when extracting to produce the same volume of raffinate with parachlorphenol the viscosity index is 88. However, when extracting with a mixture of equal parts of furfural and parachlorphenol, the viscosity index is still above 90. The same effect is observed when extracting to pro duce successively higher yields of raflinate, except that with higher yields the reduction in viscosity index of the raffinates obtained with the parachlorphenol alone is quite marked.

For example, when extracting to obtain a raffinate amounting to 70% by volume of the residuum, the raffinate so obtained with furfural alone has a viscosity index above 90, while that obtained with parachlorphenol alone has a viscosity index of only '76. However, the raffinate obtained when employing a mixture of furfural and parachlorphenol is 88, or very nearly the same as when using the furfural alone. This shows the advantage of employing a mixture of furfural and parachorphenol from the standpoint of obtaining a maximum yield of high viscosity index oil.

As already stated above, the furfural acts as an anti-solvent, offsetting the solvent action of the parachlorphenol for the more paraffinic constituents of the oil.

Thus, as indicated by the foregoing tables, it is possible to employ the solvent mixture of my invention so as to obtain from residual lubricating oil a raffinate oil of relatively low residual carbon content without sacrificing the yield of high viscosity index oil.

Thus, from a residuum of the above type, it is possible to produce a rafiinate oil amounting to 55 to 70% of the residuum, and having a viscosity index of around 90 and above with a residual carbon content of around 2 to 4%.

In practicing my invention, it is contemplated that the extraction may be carried out in either stage or continuous countercurrent contact. It is also contemplated that the extraction may be carried out in the presence of a diluent solvent, such as propane or other somewhat similar lowboiling petroleum hydrocarbon.

Where a continuous countercurrent operation is used, it is advantageous to employ a packed tower. The residuum to be treated is introduced to the lower portion of such tower, while the solvent mixture is introduced to the upper portion. The solvent and oil flow countercurrently to each other through the tower, and form extract and raffinate phases which are removed from the bottom and top of the tower, respectively.

The extract phase contains the low viscosity index constituents, residual carbon-forming constituents, and dark-colored bodies dissolved in the bulk of the solvent liquid, while the raffinate phase comprises the high viscosity index constituents substantially free from residual carbonforming and dark-colored bodies.

Where a diluent solvent is employed, it may be advantageous to introduce the residuum to a middle point of the tower while introducing the diluent to the lower portion thereof. In such a case, the solvent mixture is introduced to the upper portion of the tower. In any case, the mixture of oil and solvent is ultimately separated into extract and raffinate phases, as stated above.

As a further modification of the invention, the residual oil may be subjected to a preliminary deasphalting treatment prior to extracting with the mixture of furfural and chlorphenol. ample, the residuum may be diluted with propane in the proportion of about four or five parts of propane to one part of residuum, and the diluted mixture subjected to settling at a temperature of around F. in order to precipitate the hard asphaltic constituents. The precipitated constituents are removed, and the dilute solution of residuum in propane, containing soft or resinous asphaltic constituents, is then subjected to extraction with the mixture of furfural and chlorphenol at a temperature of around 120 F. or thereabouts, or at a different temperature if desired, in order to remove low viscosity index constituents and the remaining asphaltic and darkcolored constituents. I

While a mixture containing equal parts of parachlorphenol and furfural has been mentioned above, it is contemplated that the composition of the solvent may be varied. For example, it may be advantageous to employ a solvent mixture containing 25% to 75% by weight of furfural. The ratio of solvent mixture to oil employed in carrying out the extraction can be chosen to produce the desired degree of refining action. Usually, from one to four parts of solvent mixture to one part of oil by volume are employed.

Obviously, many modifications and variations of the invention, as hereinbefore set forth, may be made without departing from the spirit and scope thereof, and therefore only such limitations should be imposed as are indicated in the appended claim.

I claim:

In the solvent refining of residual lubricating oil containing hard and soft asphalt, dark-colored constituents, and oil of low and high viscosity index and which involves extraction of the oil with a primary selective solvent consisting of furfural, the method which comprises diluting the oil with a low boiling petroleum fraction com- For ex- I prising propane sufiicient in amount to precipitate hard asphaltic constituents, removing the precipitated hard asphaltic constituents while retaining soft asphaltic constituents in the mixture, extracting the partially deasphalted mixture with furfural in the presence of a secondary selective solvent consisting of the isomers of chlorphenol,

including ortho and para, and containing around 60 to 70% of the para isomer, forming an extract phase comprising low viscosity index, asphaltic and dark-colored constituents dissolved in the bulk of the solvent, and a raifinate phase-comprising high viscosity index oil mixed with some of the solvent, and separating the two phases.

LEON W. COOK. 

